1. Field of the Invention
The invention concerns composite seals with incorporated conductor.
2. Description of the Prior Art
It is sometimes necessary to fit elastic seals between two parts movable relative to each other, to obtain insulation or a seal. This is the case with refrigerator doors, for example.
In some applications these seals have to adapt to specific conditions of use, over and above their inherent qualities specific to their sealing function.
As is well known, for example, electronic equipment cabinets and cases, especially those of computers, acquire an electrostatic charge due to the functioning of the system that they contain and this static electricity has to be eliminated by conducting it to ground. This presupposes electrical continuity between all the associated parts: chassis, frame, support, cabinet or case. These cabinets and cases are equipped with access doors which have to receive a seal to protect the electronic system, in particular against dust in the atmosphere. If the seals are electrically insulative there is an electrical discontinuity between the cabinet and the door, as a result of which the functioning of the system may be seriously disturbed.
To avoid this seals are used that are both elastic and electrically conductive. Their manufacture has drawbacks, however.
Seals of this kind generally comprise two parts: a substantially rigid support, for example a strip of stainless steel, and a seal proper consisting of an elastic profiled member. The combination of these two heterogeneous parts presents difficulties because they cannot be glued since the adhesives currently known for this purpose are electrically insulative and prevent the electrical continuity that is an essential requirement.
To overcome this problem the profiled member is fixed to the strip without adhesive and fixing is obtained by extruding the profiled member onto the moving metal strip with the profiled member stabilized when it is applied to the strip. In practice the profiled member is made from silicone rubber and the strip/profiled member combination is passed through a vulcanizing oven.
In this way intimate and direct contact is obtained between the two conductive parts and the electrical problem is solved because there is no insulative intermediary.
It is evident that this manufacturing process has drawbacks because on the one hand the process is in itself difficult to execute using skilled labor and on the other hand it requires a complex installation, consuming large quantities of energy (the vulcanizing oven has to be heated to approximately 240.degree. Centigrade), all this resulting in a high unit cost.
The present invention remedies these disadvantages by providing an elastic seal with good electrical conductivity obtained by simple assembly of a pre-formed elastic profiled member to a metal strip.